PRODUCTION OF FEED TRAINED LARGEMOUTH BASS FINGERLINGS: NURSERY PHASE THROUGH FEED TRAINING

Largemouth bass, Micropterus salmoides, fingerlings have been produced by state and federal hatcheries since the 1890's for stocking programs. Unlike channel catfish Ictalurus punctatus and rainbow trout Oncorhynchus mykiss, newly-hatched largemouth bass fry (swim-up stage) cannot be easily trained to accept prepared diets. Therefore, bass fry are usually raised in fertilized nursery ponds until they reach 25-50 mm TL (1-2 g). Fry stocking densities in ponds are commonly 125,000-500,000 fry/ha to produce 25-50 mm fingerlings. In well managed ponds, growth rates of 1.0-1.5 mm/d and target lengths of 38 mm can be achieved in 30-45 days after fry stocking. Previously, fingerlings were then transferred to grow-out ponds where they were raised to larger sizes on forage fish. However, this extensive production method requires many ponds for bass and forage fish, as it requires approximately 5-10 kg forage fish to produce a 1 kg bass.  

Studies have examined largemouth bass production on artificial feeds since the 1960's. Today many federal, state, and private hatcheries produce 10-15 cm fingerlings on feed for stock enhancement programs and for further grow-out of food-fish. To economically produce large numbers of fish of this size requires that fingerlings be feed-trained to accept artificial feeds. This allows much higher stocking densities which produces more advanced fingerlings from finite pond resources. Feed training is the production phase where pond-reared juveniles are crowded into tanks at high densities and presented highly palatable food items at frequent intervals. Juveniles are gradually transitioned to a 100% artificial feed over 10-14 d.

Several studies have tested different initial food items, such as ground fish, fish eggs, moist pellets, and freeze dried krill for feed-training largemouth bass fingerlings. Over time, domestication of cultured stocks of largemouth bass and advances in artificial diets has improved success during feed training to the point that currently most fingerling producers do not use feeding stimulants or "training" diets. Most food fish producers purchase feed trained fingerlings from hatcheries in southern states that specialize in sportfish production for recreational pond stocking.